linux-kernel - Re: [perfmon] Re: [PATCH 1/2] Separate the performance counter allocation from the LAPIC NMI watchdog

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Message-ID: <20070621083645.GA26740@frankl.hpl.hp.com>
Date:	Thu, 21 Jun 2007 01:36:45 -0700
From:	Stephane Eranian <eranian@....hp.com>
To:	Björn Steinbrink <B.Steinbrink@....de>,
	Andi Kleen <ak@...e.de>, mingo@...e.hu,
	linux-kernel@...r.kernel.org, levon@...ementarian.org,
	perfmon@...ali.hpl.hp.com, oprofile-list@...ts.sourceforge.net,
	wcohen@...hat.com, akpm@...ux-foundation.org
Subject: Re: [perfmon] Re: [PATCH 1/2] Separate the performance counter allocation from the LAPIC NMI watchdog

Bjorn,


On Wed, Jun 20, 2007 at 02:59:33PM -0700, Stephane Eranian wrote:
> Bjorn,
> 
> I ran into one issue related with the new allocator.
> 
> In the case of a Core 2 Duo processor, the PMU implements more
> than just basic counters. In particular it supports fixed counters
> and PEBS where both use another set of MSRs. Those are not within
> a 66 bit distance from MSR_ARCH_PERFMON_EVNTSEL0. Thus the allocator
> fails with an assertion.
> 
> I do know that perfmon is the only consumer of those extended 
> features TODAY. Yet I think we need to define the allocator such
> that it can work with other "distant" MSRs as well.
> 

I think that a workaround for this issue could be for the allocator
to grant the requests for registers outside of the range, i.e., register
that it does not see/manage.

> On Wed, Jun 20, 2007 at 08:33:15PM +0200, Bj?rn Steinbrink wrote:
> > On 2007.06.20 15:01:02 +0200, Andi Kleen wrote:
> > > 
> > > > Once this is fixed (which is what Bjorn did), then I will agree with you.
> > > > For this, the allocator needs to be able to probe the CPU and initialize
> > > > its own data structures.
> > > 
> > > Ok that sounds reasonable. Please someone send a patch that does only 
> > > that.
> > 
> > OK, here come the bugfixes without any restructuring. The first patch
> > enables unconditional probing of the watchdog. The second makes the
> > perfmon nmi watchdog reserve the correct perfctr/evntsel.
> > 
> > Björn
> > 
> > -------------------------------------------------------------------------
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> 
> -- 
> 
> -Stephane
> _______________________________________________
> perfmon mailing list
> perfmon@...ux.hpl.hp.com
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-- 

-Stephane
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